Real-Time Leaf-Level Vapor Pressure Deficit Monitoring: Development, Uncertainty Analysis, and Validation of a Low-Cost Portable Sensor Platform for Controlled Environment Agriculture
Applied Sciences (Switzerland), cilt.16, sa.17, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 16 Sayı: 17
- Basım Tarihi: 2026
- Doi Numarası: 10.3390/app16178625
- Dergi Adı: Applied Sciences (Switzerland)
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Applied Science & Technology Source, Compendex, INSPEC, Directory of Open Access Journals
- Anahtar Kelimeler: controlled environment agriculture, leaf temperature, low-cost sensors, portable measuring device, uncertainty analysis, vapor pressure deficit, vertical farming
- Ankara Üniversitesi Adresli: Evet
Özet
Leaf-level vapor pressure deficit ((Formula presented.)) depends on the temperature of the leaf surface as well as the temperature and humidity of the surrounding air. Therefore, instruments that estimate (Formula presented.) from a fixed leaf–air temperature offset may introduce condition-dependent errors. This paper presents the development, uncertainty analysis, and validation of a low-cost, single-housing, portable sensor platform that directly measures air temperature ((Formula presented.)), relative humidity ((Formula presented.)), and leaf surface temperature ((Formula presented.)) via an SHT35 and an MLX90614 infrared thermometer, and computes (Formula presented.) on-board in real time using an ATmega328-based microcontroller. The platform was validated against a Testo 610 thermo-hygrometer and a FLIR E4 thermal camera on two lettuce (Lactuca sativa L.) cultivars grown at 20–26 °C and 40–70 %RH. Coefficients of determination were (Formula presented.) for (Formula presented.) and (Formula presented.) for (Formula presented.) ((Formula presented.)). Leaf temperature and the on-board (Formula presented.) output itself were validated against reference readings taken during randomly timed site visits on three separate days ((Formula presented.) after excluding apparent misreads): (Formula presented.) showed (Formula presented.) against the FLIR E4, and the device-computed (Formula presented.) showed (Formula presented.) against a reference (Formula presented.) computed from the same reference readings, with a mean bias of (Formula presented.) kPa and an RMSE of (Formula presented.) kPa. A propagation-of-error analysis separately yielded a worst-case (Formula presented.) uncertainty of (Formula presented.) kPa under representative conditions ((Formula presented.) °C, (Formula presented.) °C, (Formula presented.)), mainly driven by the (Formula presented.) °C infrared sensor tolerance; the empirically observed error was well within this conservative bound. With a cost of USD 83.28, this platform provides a practical and economically accessible tool for real-time monitoring and VPD-informed decision making in vertical farms and greenhouses.